Method for making hollow bevel gears with integral hollow shaft

ABSTRACT

A solid bevel gear with integral solid shaft is provided as a blank and a core is extruded from this blank by means of an extrusion punch acting through the shaft end of the blank, using a die that supports the bevel gear in contour fitting relation as to the teeth and having a bore of diameter smaller than the punch through which the core is extruded. The core is subsequently removed.

United States Patent 11 1 Burgdorf METHOD FOR MAKING HOLLOW BEVEL GEARSWITH INTEGRAL HOLLOW SHAFT Miirten Burgdorf, Ruckersdorf, GermanyKabel-und Metallwerke Gutehoffnungshutte Aktiengesellschaft, Hannover,Germany Filed: Aug. 24, 1972 Appl. No.: 283,520

Inventor:

Assignee:

[30] Foreign Application Priority Data Sept. 2, 1971 Germany P 21 44006.2

US. Cl 29/1591, 29/D1G. 47, 72/358, 74/4595 Int. Cl B21d 53/28, B21h5/00, B21k 1/30 Field of Search 1. 29/1592, 159 R, 29/D1G. 47; 72/358,267; 74/4595 References Cited UNITED STATES PATENTS 9/1920 Paque 72/354[4 1 Dec. 25, 1973 2,964,838 12/1960 Schober 1. 29/1592 3,298,219 1/1967Schober 29/1592 X OTHER PUBLICATIONS Alien Property CustodianPublication, Serial No. 191, 168, Published April 27, 1943, FritzSinger.

Primary ExaminerRichard .1. Herbst Assistant ExaminerV. A. DipalmaAtt0rneyRa1f H. Siegemund [57] ABSTRACT 3 Claims, 1 Drawing FigureMETHOD FOR MAKING HOLLOW BEVEL GEARS WITH INTEGRAL HOLLOW SHAFTBACKGROUND OF THE INVENTION The present invention relates to a processof making bevel gears by means of metal working. The gear to be made isto have a body having configuration of a hollow truncated cone with ahollow shaft extending from the larger axial surface of the cone. Moreparticularly, the invention relates to improvements in such processeswherein the gear is made through cold working a blank so as to obtainthe desired configuration, and wherein the teeth extend from thefrusto-conical body.

Bevel gears are used, for example, in the art of automotive engineeringand here, particularly, in the gearing for the rear axle. The borethrough the shaft receives that axle and is usually provided withsplines. In view of the rather complex configuration of such gear,

it seems obvious to make the basic body configuration first throughconventional cold working, and to form the teeth separately; e.g.,through press working.

Developing the latter thought further, one could, for example, startwith a cylindrical blank which has been upset on one side to obtain aconical configuration. Then a bore is made through shallow forming andpiercing. Finally, teeth are pressed into and from the cone. To proceedalong this line means to follow the state of the art. However, bevelgears of satisfactory quality cannot be made through this application ofconventional principles.

7 In order to fill completely the teeth-defining cavities in the die,the press working and extrusion process must proceed from the smalldiameter of the cone. Thus, upon planning production, the changes inconfiguration leading from the blank to the final bevel gear must notoccur in an arbitrary sequence. Rather, the following rules must beobserved:

The intermediate product used as blank for the tooth forming processmust permit filling of the bevel gear die in direction from the smalldiameter. Thus, this particularblank must not have a bore. If thisintermediate blank has already an axial bore, the material will flowradially outwardly as the press ram or punch advances. Consequently, theblank will be deformed to have an outwardly bulging configurationresulting in an overlap at the bore during repressing the teeth. As thedimensions and tolerances of the already completed teeth must bemaintained, subsequent forming steps must not move material into theregion of these teeth. However, precisely that does occur when thehollow shaft portion is made through inverted extrusion whereby theteeth have to be held in a toothed die element. Therefore, it waspreviously necessary to make the bore subsequent to the cold workingprocess of the gear and by means of cutting, such as drilling.Obviously, bevel gear with long shafts are very expensive to make inthis manner and the process is also quite time consuming.

DESCRIPTION OF THE INVENTION It is an object of the present invention tomake hollow bevel gears with integral hollow shaft by means of a processwhich is more economical than the known methods as previously practiced.It is a particular object of the invention to make bevel gears withintegral hollow shaft by means of cold working process that does notrequire machining in spite of the relatively complex configuration.

In accordance with the present invention, it is suggested to provide abevel gear first through cold working, such as extrusion molding, but insolid configuration and with a solid integral shaft extending from theside with larger diameter of the gears. Subsequently, a bore is formedin the gear and shaft in that a core is extruded, beginning from theshaft end and as a direct extrusion process out of the gear through thefront face of smallest diameter thereof, whereby the extruded core hasslightly smaller diameter than the bore cold worked by the punch intothe shaft. Thus, machining is not involved to obtain the bore, nor isthere the drawback resulting from using hollow blanks.

For practicing the invention, a die is used having contoured cavitycorresponding to the bevel gear teeth. The die has a bore beginning inthe small diameter bottom of the die cavity, and having diameter smallerthan the diameter of a punch acting from above for extruding a core fromthe bevel gear for obtaining the bore therethrough. Preferably, the dieis provided with a conical extrusion shoulder where facing the punch.This shoulder was found to increase the life of the die, and it improvesthe extrusion flow conditions.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject w matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood from the following description taken inconnection with the accompanying drawings in which:

The FIGURE illustrates a die and punch for making a hollow bevel gear,showing the beginning of the process of bore making to the left, andshowing a phase close to completion to the right of a central dividingline.

DESCRIPTION OF THE DRAWING Proceeding now to the detailed description ofthe drawing, the left-hand position shows an intermediate product likeblank 1 comprised of a body 2 of frustoconical configuration with anintegral, short shaft 3. Blank 1 has solid configuration and body 2 isalready provided with teeth 4.

This blank 1 is placed into a die 5 having particularly a contour so asto matingly receive the teeth 4, crest, flank and root, in accuratecontour fitting relation. A sleeve 7 serving as plunge guide is placedonto the die 5 to supplement the die 5 as far as shaft 3 is concerned.The sleeve tightly receives the shaft and accordingly covers the die 5completely.

The die 5 is provided with a bore 8 in the bottom and where facing thesmall diameter front face of the bevel gears. The bore 8 has diametersmaller than an extrusion punch 6. Bore 8 has a conical shoulder 10 atits upper end and is continued down in a bore 11 of somewhat largerdiameter.

In operation, plunger or punch 6 is lowered (righthand side). The punchhas diameter corresponding to the diameter of the bore to be made inblank 1. As the punch 6 engages the blank, and thereafter upon continueddown movement of the punch, a core is extruded in that material in theinterior of blank 1 flows out at the lower end of blank 1 and into bore8. In essence,

the extruded core 9 is reduced. Core 9 is removed separately uponcompletion of extrusion.

Conical shoulder 10 improves the flow conditions from the blank into thecore, and the shoulder also avoids damage to this upper edge of bore 8.As stated, bore 8 has somewhat smaller diameter than punch 6, and theresulting bore in shaft and gears. This is necessary, as otherwise thematerial would not flow but break off. It can readily be seen that thecentrally limited extrusion process does not disturb the configurationof the teeth as they have been formed previously, and the teeth arecontour fittedly supported in die 5.

The invention is not limited to the embodiments described above but allchanges and modifications thereof not constituting departures from thespirit and scope of the invention are intended to be included.

I claim:

1. Method for making bevel gear with integral hollow shaft extendingfrom the larger diameter surface of a frusto-conical body from whichextends the teeth of the gears, comprising the steps of:

making a bevel gear with integral solid shaft by means of cold workingincluding making a frustoconical body with bevel gear teeth; andextruding from the bevel gear as a blank, a core through the smalldiameter surface of the bevel, through operation of a punch of largerdiameter than the extruded core and acting on and through the integralshaft to obtain a bore therein.

2. Method as in claim 1, using a supporting die having contour matchingconfiguration for supporting the blank and having an aperture in thebottom smaller than the diameter of the extrusion plunger.

3. Method as in claim 2, using a die wherein said aperture has abevelled shoulder.

1. Method for making bevel gear with integral hollow shaft extendingfrom the larger diameter surface of a frusto-conical body from whichextends the teeth of the gears, comprising the steps of: making a bevelgear with integral solid shaft by means of cold working including makinga frusto-conical body with bevel gear teeth; and extruding from thebevel gear as a blank, a core through the small diameter surface of thebevel, through operation of a punch of larger diameter than the extrudedcore and acting on and through the integral shaft to obtain a boretherein.
 2. Method as in claim 1, using a supporting die having contourmatching configuration for supporting the blank and having an aperturein the bottom smaller than the diameter of the extrusion plunger. 3.Method as in claim 2, using a die wherein said aperture has a bevelledshoulder.